Today, electric power and electronic technology are being developed towards high frequency, high power and high power density. In the high power converters (with power levels from several hundred Kw to several Mw), the high frequency is embodied in selection of higher switch frequencies (form several kHz to several tens of kHz), the high power is embodied in selection of the power modules (IGBT/IGCT, etc.) with higher rating currents, and the high power density means higher power to be obtained per unit bulk, i.e., under the same power level, the bulk of the converter is made smaller.
Consequently, more and more new technologies are applied to the high power converters, such as using a plurality of IGBT modules connected in parallel to achieve higher current output (namely, higher power under the same output voltage), using the laminated bus bars to reduce the inner stray inductances of the DC-link capacitors as well as the stray inductances between the DC-link capacitors and the IGBT power modules, and the like.